This invention provides a very easy and simple way to kill and monitor bacteria, and multidrug resistant bacteria in particular.
1. Conventional Ways to Kill Bacteria
1.1 Antibiotics—
A drug is used to treat infections caused from bacteria and other microorganisms. Originally, an antibiotic is a substance produced by one microorganism that selectively inhibits the growth of another. Synthetic antibiotics, usually chemically related to natural antibiotics, have been produced that accomplish comparable tasks. In 1926, Alexander Fleming discovered penicillin, a substance produced by fungi that appeared able to inhibit bacterial growth. In 1939, Edward Chain and Howard Florey further studied penicillin and later carried out trials of penicillin on humans (with what were deemed fatal bacterial infections). Fleming, Florey and Chain shared the Nobel Prize in 1945 for their work which ushered in the era of antibiotics. Another antibiotic, for example, is tetracycline (brand names: Achromycin and Sumycin), a broad-spectrum agent effective against a wide variety of bacteria including Hemophilus influenzae, Streptococcu pneumoniae, Mycoplasma pneumoniae, Chlamydia psittaci, Chlamydia trachomats, Neisseria gonorrhoea, and many others. The first drug of the tetracycline family, chlortetracycline, was introduced in 1948.
The most widely known antibiotic is perhaps penicillin, famously made from mold. When it was introduced, many of the sexually transmitted diseases such as gonorrhea went from being a shameful and life changing event to an embarrassing trip to the doctors. One of the most prevalent and unstoppable myths about antibiotics is that they can cure a cold. Antibiotics work against bacterial infections, and colds are caused by viruses—therefore, a course of antibiotics will do nothing but perhaps kill off the body's own population of beneficial bacteria, leaving the cold to run its natural course. Nevertheless, patients often pressure their doctors into prescribing antibiotics when they come down with a cold or the influenza.
1.2 Autoclave—
An autoclave is a device used to sterilize equipment and supplies by subjecting them to high pressure (1.2-1.5 kg cm−2) saturated steam at 121° C. for around 15-20 minutes depending on the size of the load and the contents. It was invented by Charles Chamberland in 1879, although a precursor known as the steam digester was created by Denis Papin in 1679. The name comes from Greek auto-, ultimately meaning self, and Latin clavis meaning key—a self-locking device. Autoclaves are widely used in microbiology, medicine, tattooing, body piercing, veterinary science, mycology, dentistry, chiropody and prosthetics fabrication. They vary in size and function depending on the media to be sterilized. Typical loads include laboratory glassware, other equipment and waste, surgical instruments and medical waste. A notable growing application of autoclaves is the pre-disposal treatment and sterilization of waste material, such as pathogenic hospital waste. Machines in this category largely operate under the same principles as conventional autoclaves in that they are able to neutralize potentially infectious agents by utilizing pressurized steam and superheated water. A new generation of waste converters is capable of achieving the same effect without a pressure vessel to sterilize culture media, rubber material, gowns, dressing, gloves, etc. It is particularly useful for materials which cannot withstand the higher temperature of a hot air oven. Autoclaves are also widely used to cure composites and in the vulcanization of rubber. The high heat and pressure that autoclaves allow help to ensure that the best possible physical properties are repeatably attainable.
2. Biological Templates
2.1 Viral Templates—
Viruses are generally composed of proteinaceous shell (capsid) surrounding genomic material. One such template, viruses, exhibits the characteristics of an ideal nanobuilding block, monodispersity, site-specific heterogenerous surface chemistry accessible interior, and extensive chemical tailorability. They offer a suite of beneficial characteristics for the synthesis of metallodielectric nanoshells, including a number of morphologies (spheres, rods, and tubules) that are absolutely monodisperse and both external and internal surfaces that are chemically addressable by a broad range of organic and inorganic chemistries. For example, amino acids on the surface of the capsid, such as cystine, glutamic acid, and aspartic acid, present amine, carboxylate, and thiol groups that are amenable to complexation with metal nanoparticles (NPs). A capsid can also be easily modified to present additional thiol groups on the particle surface.
The use of a virus core and adaptation of the aforementioned chemistries to the growth of metal nanoshells are discussed herein. Utilization of a native virus and the inherent chemical functionality of the capsid affords the ability to grow and harvest biotemplates in large quantities. These natural templates simplify the preparation of the dielectric core particle and provide a narrower size distribution and accessible core sizes below 80 nm. Furthermore, upon removal of the core genetic material, the resultant virus-like particle provides a hollow shell, enabling facile incorporation of various electrooptic molecules within the center of the nanoshell and thus accessing the local field enhancements within as well as at the surface of the nanoshell.
Toward these objectives, the first metallic nanoshells based on bioscaffolds are produced using Chilo iridescent virus (CIV) as the dielectric core. In 2005, Radloff et. al. utilized CIV to demonstrated as a useful core substrate in the fabrication of metallo dielectric, plasmonic nanostructures. An gold (Au) shell is assembled around the wild-type viral core by attaching small NPs to the virus surface by means of the chemical functionality found inherently on the surface of the proteinaceous viral capsid. The density of these nucleation sites was maximized by reducing the repulsive forces between the Au particles through electrolyte addition. These Au NPs then act as nucleation sites for the electroless deposition of Au ions from solution around the biotemplate. The optical extinction spectra of the metalloviral complex is in quantitative agreement with Mie scattering theory. Overall, the utilization of a native virus and the inherent chemical functionality of the capsid afford the ability to grow and harvest biotemplates for metallodielectric nanoshells in large quantities, potentially providing cores with a narrower size distribution and smaller diameters (below 80 urn) than for currently used silica.
Au shell growth around CIV cores is demonstrated using modifications to previous established fabrication routes. By decreasing the surface charge of the capsid through controlled introduction of excess electrolyte, maximization of the nonselective attachment of Au NPs to the capsid surface enabled the growth of a complete Au shell around CIV. The resulting metallodielectric nanoshell exhibited a dipole resonance in the near infrared region. The inherent surface chemistries of the wild-type viral capsid of CIV enabled a facile fabrication route for metallodielectric assembly. This is in contrast to virus-like particles where genetic engineering of the capsid and subsequent protein expression and assembly limit scaffold supply and significantly increase preparation and processing concerns. More extensive understanding of the amino acid distribution on the viral surface of the chosen capsid, rather than site-specific mutation, will improve the ability to form smooth shells through use of specific rather than nonspecific seed-capsid interaction.
2.2 Fungous Templates—
Micro-organisms, including viruses, bacteria, and fungi, grow into unique and structurally interesting forms that have been used by many researchers as templates for the self-organization of inorganic materials with the aim of realizing functional macrostructures. In such assemblies, the inherent uniformity of the biological structures can be combined with the functional properties of inorganic NPs (such as conductivity and optical activity) to realize functional macrostructures. As an example, a dense assembly of NPs on filamentous fungi, with typical hyphal diameters of the order of a few micrometers (varying from species to species) and lengths varying from tens of micrometers to a few millimeters could find immediate applications as circuit components. Most reports on the assembly of inorganic materials on micro-organisms such as viruses, bacteria, and fungi involve complex biological molecules, for example DNA or proteins, facilitating their attachment to the biological surface, either by the sequence-specific recognition properties of DNA strands, or protein recognition.
In 2007, Sugunan et. al. reported a facile route, based on simpler chemistries, for the self-organization of colloidal Au NPs on living filamentous fungi to fabricate Au microstructures with typical widths of several micrometers and lengths exceeding a few millimeters. The process involves synthesis of Au NPs using monosodium glutamate to reduce chloroauric acid, resulting in the formation of colloidal particles stabilized by glutamate ions. Fungal conidia are then added and allowed to grow in the colloidal medium. The physiological process of absorption of nutrients by the fungus, consisting mainly of unreacted precursors (excess glutamate ions) from the reduction-precipitation reaction for the synthesis of the Au NPs, drives the assembly of the NPs. The agglomeration and accumulation of colloidal NPs lead to the formation of a thick coating on the hyphal walls, which exhibit the optical properties of bulk gold. The assemblies so formed can be then modified into micro-ribbon-like and microtubular morphologies by post-fabrication treatment.
This process of self-assembly of NPs on growing filamentous fungi has the potential to be extended to other NPs and micro-organisms. In principle, any micro-organism that can survive on simple nutrients (such as bacteria, which can survive with only glutamates as nourishment) can act as templates, while the weak ligand-particle interaction (typical for charge-stabilized NPs of any material) and the consequent sensitivity to the ionic content in the dispersant medium can drive the organized agglomeration. Thus, by engineering the dispersant solution with the required nutrients, the described process has the potential to be extended to the self-assembly of chargestabilized colloidal NPs of a wide range of materials into novel structures, utilizing the symmetry and structural shapes dictated by micro-organisms.
2.3 Bacterial Templates—
Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometers in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. There are broadly speaking two different types of cell wall in bacteria, called Gram-positive and Gram-negative. The following characteristics are generally present in a Gram-positive bacterium, a. cytoplasmic lipid membrane; b. thick peptidoglycan layer: teichoic acids and lipoids are present, forming lipoteichoic acids, which serve to act as chelating agents, and also for certain types of adherence; c. capsule polysaccharides (only in some species); d. flagellum (only in some species), if present, it contains two rings for support as opposed to four in Gram-negative bacteria because Gram-positive bacteria have only one membrane layer. e. The individual peptidoglycan molecules are cross-linked by pentaglycine chains by a DD-transpeptidase enzyme. In Gram-negative bacteria, the transpeptidase creates a covalent bond directly between peptidoglycan molecules, with no intervening bridge. On the other hand, Gram-negative bacteria was displayed some characteristics as follows, a). cytoplasmic membrane; b). thin peptidoglycan layer (which is much thicker in Gram-positive bacteria); c). outer membrane containing lipopolysaccharide (LPS, which consists of lipid A, core polysaccharide, and O antigen) in its outer leaflet and phospholipids in the inner leaflet; d). porins exist in the outer membrane, which act like pores for particular molecules; e). there is a space between the layers of peptidoglycan and the secondary cell membrane called the periplasmic space; f). the S-layer is directly attached to the outer membrane, rather than the peptidoglycan; if present, flagella have four supporting rings instead of two; g). no teichoic acids or lipoteichoic acids are present; h). lipoproteins are attached to the polysaccharide backbone; i). most of them contain Braun's lipoprotein, which serves as a link between the outer membrane and the peptidoglycan chain by a covalent bond; j). most do not sporulate.
Bacteria could be of help or endanger to human being, animals and environment. It is known that bacteria could be utilized to cure some diseases and ailments, for instance, cloning of molecular biology, photo synthetic bacteria, etc. However, the interaction of Au with the systems of microorganism has been a topic of interest in widely divergent fields. Integrating biology into materials research to bring forward significant advances in microfabrication resulting in functional structures at the nano-, and micro-scale is still under research.